CodeForces 374A. Divisible by Seven

构造。。。。

A. Divisible by Seven

time limit per test
1 second

memory limit per test
256 megabytes

input
standard input

output
standard output

You have number a, whose decimal representation quite luckily contains digits 1, 6, 8, 9. Rearrange the digits in its decimal representation so that the
resulting number will be divisible by 7.

Number a doesn't contain any leading zeroes and contains digits 1, 6, 8, 9 (it also can contain another digits). The resulting number also mustn't contain
any leading zeroes.

Input

The first line contains positive integer a in the decimal record. It is guaranteed that the record of number a contains
digits: 1, 6, 8, 9. Number a doesn't contain any leading zeroes. The decimal representation of number a contains
at least 4 and at most 106 characters.

Output

Print a number in the decimal notation without leading zeroes — the result of the permutation.

If it is impossible to rearrange the digits of the number a in the required manner, print 0.

Sample test(s)

input

1689

output

1869

input

18906

output

18690

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <algorithm>

using namespace std;

bool sh[10010000];

int main()
{
string str;
int cnt = 0, mod = 0;
cin >> str;
int n = str.size();
memset(sh, true, sizeof(sh));
bool n1 = false, n6 = false, n8 = false, n9 = false;
for (int i = 0; i < n; i++)
{
int b = str[i] - '0';
if (b == 0)
{
sh[i] = false;
cnt++; continue;
}
if (b == 1 && !n1)
{
n1 = true;
sh[i] = false;
continue;
}
if (b == 6 && !n6)
{
n6 = true;
sh[i] = false;
continue;
}
if (b == 8 && !n8)
{
n8 = true;
sh[i] = false;
continue;
}
if (b == 9 && !n9)
{
n9 = true;
sh[i] = false;
continue;
}
mod = (mod * 10 + b) % 7;
}
mod = (mod * 10000) % 7;
for (int i = 0; i < n; i++)
{
if (sh[i]) putchar(str[i]);
}
if (mod == 0)
{
printf("1869");
}
else if (7 - mod == 1)
{
printf("1968");
}
else if (7 - mod == 2)
{
printf("1689");
}
else if (7 - mod == 3)
{
printf("6198");
}
else if (7 - mod == 4)
{
printf("1698");
}
else if (7 - mod == 5)
{
printf("1986");
}
else if (7 - mod == 6)
{
printf("1896");
}
while (cnt--)
{
putchar('0');
}
///system("pause");
return 0;
}